Ok, so I'm have having issues with brake master cylinder but its seems slightly different than what I've in the threads and almost like I have of an electrical issue maybe that may or may not be solved by replacing the whole master cylinder.
(for context its a 1999 LC with 572,000 miles)
This past Tuesday on a fairly warm morning my wife turned the car on, the brake motor came on normal but after 20 or so seconds got a bit louder with a bit of screeching/whistling sound (not quite as loud or constant as the screaming seagull sound I've heard on others videos) and the abs and brake light go on and off about 1.5 seconds but no alarm. Later that day I pumped the brakes 30 times and turned the key to on (without starting) and got the same intermittent screech and slowly blinking lights, if I tap the pedal during this it cuts off the noise from the brake motor/accumulator and the lights but then they come back.
I have checked and there are no bubbles and splashing of fluid when the screeching happens or when the motor/booster is on. It seems more like an issue with the high pressure switch. I also audibly hear a clicking (tick/tock) sound that seems almost like it is coming from the fuse box/or maybe abs box. None of the fuses look blown, but not sure about the relays. I only have a scan gauge II and a $25 code reader from amazon and neither show any codes. I'm guessing if there is ABS sensor/solenoid/fuse issues it would show up on these devices? Do I need techstream or just a better code reader? I did replace the passenger side CV on saturday, maybe I knocked the abs sensor?
I did have an issue at the end of December where on a road trip with the family the flare nut going into the three way junction on top of the rear was leaking and I had a shop cut it, reflare, and flush the brakes, and it does look like they overfilled the reservoir (and most likely not with toyota fluid). It looks like it may have over flowed since then and maybe the hygroscopic issues are affecting the wiring for the master cylinder. If that's the case it would seem replacing the whole MC assembly would take care of it.
I'm trying to figure out how I can be sure the master cylinder vs an electrical problem elsewhere (rain egress in the a pillar getting on wiring, abs sensor, fuses/relays, etc)?